Leitrim Group

The Leitrim Group is a lithostratigraphical term coined to refer to the succession of rock strata which occur in Northern Ireland within the Visean and Namurian stages of the Carboniferous Period.

This Asbian to Brigantian age formation varies from 45m to 80m thick and consists largely of sandstones and shales with lesser amounts of siltstone and limestone.

From its top downwards, it is divided into the Corry, Sheena Shale, Glenkeel, Doobally Sandstone, Drummangarvagh, Lugasnaghta, Sraduffy, Larkfield and Tullyskeherny members.

Referred to as the Yoredale Sandstone in the late nineteenth century, this Asbian age sequence varies from 4m thick in County Leitrim to as much as 350m in the north of its range.

In places it sits directly on the Dartry Limestone where the Meenymore Formation rocks are missing due to the locally high relief of the underlying erosive surface.